This invention relates to one-liquid adhesive compositions comprising a non-reactive thermoplastic polyurethane resin, an acrylic monomer, a polymerizable acid monomer, a free radical polymerization catalyst having dispersed therein pressure-rupturable microspheres encapsulating an activator for said catalyst.
In copending application, Ser. No. 586,655 now U.S. Pat. No. 3,994,764, previously referred to, a two-liquid adhesive composition is disclosed comprising one solution of a polyurethane polymer plus polymer precursors, as in the present application, and a solution of polymerization catalyst activators. In joining a pair of mating surfaces, one surface may be coated with the polymer and prepolymer solution and the other with the activator solution and thereafter placing the surfaces in contact until the adhesive cures. Alternatively, one surface may be coated with both solutions, if desired.
The present invention eliminates the necessity for two solutions by encapsulating the catalyst activator in pressure-rupturable, substantially insoluble microspheres and dispersing the spherucles or beads in the polymer and prepolymer solution. The resultant one-liquid adhesive dispersion has a long shelf and pot life and is convenient to apply. In use, when it is desired to join two surfaces, one merely coats one surface with the adhesive dispersion, places the other surface in contact with the first, applies pressure to rupture the microspheres, and allows the sufficient curing time.
It is an object of this invention to provide a one-liquid adhesive composition and a method for using the same, said composition being capable of bonding a wide diversity of materials, with high strength joints both with respect to shear strength and peel strength, which attains bond strength rapidly, which requires no solvent or other volative ingredient, which has a long shelf life and pot life, which is effective with minimal or no surface preparation and which requires no expensive or elaborate equipment for use.
It is a further object of this invention to provide an adhesive dispersion and a method for using the same, the adhesive being comprised of (a) a solution of a non-reactive thermoplastic polyurethane resin, an acrylic and/or methacrylic monomer other than the acids, a co-polymerizable acid monomer, and a polymerization catalyst; and (b) pressure-rupturable microspheres or beads essentially insoluble in (a) having encapsulated therein an activator for the polymerization catalyst.
Further objects will become apparent from the following description and claims.